Since the use of magnetic elements for high-frequency applications in reading/writing heads, micro-inductors, micro-transformers or the like is spreading and magnetic thin films having good high-frequency characteristics in GHz bands are also demanded in recent years, related research and development are also positively being undertaken. Using magnetic thin films in high-frequency bands requires electric resistance of thin films to be increased so as to reduce eddy current and increase the resonance frequency. As a method of increasing the resonance frequency, anisotropic magnetic field Hk or saturation magnetization Ms may be increased, but it is generally difficult to increase Hk and Ms simultaneously and Hk and Ms are in a trade-off relationship. However, in recent years, it has been made possible to increase uniaxial magnetic anisotropy based on shape effects of crystal by causing sputtered particles to diagonally impinge on and to be oriented to a substrate using a sputtering method or ion beam method and thereby increase Hk while keeping high Ms.
An object of a diagonal incidence of sputtered particles as described above is to generate shape magnetic anisotropy within a film through the diagonal incidence and to provide high magnetic anisotropy. What becomes important here is:
[1] How to suppress variations in magnetic anisotropy.
[2] To what extent the magnetically easy axis (magnetically hard axis) should be aligned.
This is because since head chips are cut out in large quantity from a single wafer, if there are large variations in the above two aspects within the wafer surface, the performance of the individual cut heads becomes nonuniform.
In the current diagonal incidence film deposition of sputtered particles, when volume production is taken into consideration, sputtered particles having various angles of incidence arrive at a substrate and the various angles of incidence produce variations in magnetic anisotropy.
<Case 1>
For example, in the film deposition to uniformalize angles of incidence of sputtered particles, a collimator 1 may be arranged between a target 2 and a substrate 4 as shown in <case 1> of FIG. 1. In this way, selecting a direction of incidence of sputtered particles 3 generated from the target 2 allows highly uniform film deposition. However, this method causes the number of arriving sputtered particles 3 to decrease, resulting in a decrease in productivity.
<Case 2>
When the diameter of the collimator 1 is increased as shown in <case 2> of FIG. 1, sputtered particles 3 impinge on the substrate 4 from various directions. Therefore, variations in magnetic anisotropy may be produced but there is an expectation for volume production.
<Case 3>
However, in the case of <case 2>, uniform film deposition over the entire surface of the substrate 4 requires the substrate 4 or target 2 to be moved. In this case, the angle of incidence of sputtered particles 3 on the substrate 4 varies depending on the relative positional relationship between the target 2 and substrate 4. That is, when the target 2 is fixed and the substrate 4 is moved as shown in <case 3> of FIG. 1, the angle of incidence of sputtered particles 3 may increase or decrease depending on the position of the moving substrate 4. Thus, the variations in the angle of incidence of sputtered particles 3 cause variations in magnetic anisotropy of the film formed on the substrate 4.
The “angle of incidence” in the present specification denotes an angle formed by the normal line of the substrate, which is the film deposition target on which sputtered particles impinge, and the direction of incidence of incident sputtered particles. Therefore, a “low angle of incidence” is an angle of incidence when the inclination of the direction of incidence of sputtered particles from the normal line of the substrate is relatively small, while a “high angle of incidence” is an angle of incidence when the inclination of the direction of incidence of sputtered particles from the normal line of the substrate is relatively large.
The reason why variations are produced in magnetic anisotropy depending on the angle of incidence is that the direction of magnetically easy axis (magnetically hard axis) or magnitude (Hk) of anisotropic magnetic field greatly depends on the angle of incidence.
For example, as shown in FIG. 2, when the angle of incidence of sputtered particles 5 ranges from 10° to 70°, a magnetically easy axis 6 is formed in the direction perpendicular to the direction of incidence. On the other hand, when the angle of incidence of sputtered particles 5 is 70° or more, the magnetically easy axis 6 is formed parallel to the direction of incidence. That is, since the direction of magnetically easy axis changes depending on the angle of incidence of incident sputtered particles of which the magnetic film is made up, which eventually influences a skew dispersion angle (definition: angle deviation width of magnetically easy axis).
Patent Document 1 discloses a technique of controlling anisotropy of a ferromagnetic film formed using a carousel type sputtering apparatus. To be more specific, the direction and magnitude of magnetic anisotropy are controlled by disposing a mask whose width of aperture is changeable between a magnetic target and a rotating substrate holder and changing the width of aperture of the mask.
Furthermore, Patent Document 2 discloses a method for depositing an insulating thin film on a magnetic head and uniformly forming the insulating thin film over a large surface area. FIG. 3 is a schematic view of a deposition apparatus disclosed in Patent Document 2. The deposition apparatus shown in FIG. 3 is provided with a chamber 11 that houses a first ion beam gun 12, a second ion beam gun 13, a target holder 14 and a substrate support body 16.
The substrate support body 16 has a turn table 16a which is rotatable about a shaft 16b (around an axis 21a) and a substrate mount 16c which is rotatable about an axis 21b. A substrate 17 for depositing a target member thereon can be disposed on the substrate mount 16c. On the other hand, the target holder 14 is configured to be swingable in the direction of an arrow 22 and allows a target 15 to be mounted.
The first ion beam gun 12 is disposed so that an ion beam 18 impinges on the target 15 and the ion beam 18 causes the target member to be diffused from the target 15 in random directions 20. Furthermore, the second ion beam gun 13 is provided so as to cause another ion beam 19 to impinge on the substrate 17 during the deposition process.
According to the method disclosed in Patent Document 2, it is possible to achieve a uniform film thickness on the substrate 17 by appropriately rotating the target holder 14, turn table 16a and substrate mount 16c in the above configuration.    Patent Document 1: Japanese Patent Application Laid-Open No. H7-54145    Patent Document 2: Japanese Patent Application Laid-Open No. H8-296042